Add STRUCT/ARRAY and UDF support (BigQuery)

[wouter]

• Allow testing of STRUCT/ARRAY fields using TO_JSON_STRING() using options
• Allow BigQuery UDF definitions to be set using options

[daniel-bartley]

this package needs to be forked

[psousa50]

This was implemented in our latest release (0.4.0). We used a slightly different approach but your PR was very inspiring for us to implement the feature.

Thank you!